Cleanscapes CNG Plant Earthquake Drainage Design

Client: Cleanscapes, Inc. Location: Seattle, WA Contact for geotechnical projects: John Peterson

Project Background & Challenges

Cleanscapes, Inc. wanted to develop a property into a compressed natural gas (CNG) fueling facility to service its new fleet of solid waste collection trucks. The South Seattle site near the Duwamish River is in an area with weak soil and liquefaction hazards and the equipment for the facility is sensitive to settlement.

Solution

To support development and mitigate liquefaction hazards, Aspect completed a geotechnical study then specified and designed an earthquake drain system to reduce settlement to an acceptable tolerance. The drains were installed vertically on a grid throughout the part of the facility where liquefaction risks are greatest. After the drains were installed, a stone reservoir layer was placed to provide storage of water ejected by the drains in an earthquake. Conventional crushed rock base and foundation pads were then placed on the stone reservoir, providing stable support of the facility.